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<html>

<head>
  <meta charset='utf-8'>
  <meta name='viewport' content='width=device-width, initial-scale=1, user-scalable=no'>
  <meta name='mobile-web-app-capable' content='yes'>
  <meta name='apple-mobile-web-app-capable' content='yes'>
  <link rel='icon' type='image/png' sizes='32x32' href='../favicon-32x32.png'>
  <link rel='icon' type='image/png' sizes='96x96' href='../favicon-96x96.png'>
  <link rel='stylesheet' href='../css/common.css'>

  <title>Projection Layer with Multiview</title>
</head>

<body>
  <header>
    <details open>
      <summary>Projection Layer with Multiview</summary>
      <p>
        This sample demonstrates a simple technique to reduce the number of
        state changes an application needs to make while rendering, potentially
        enabling better performance.
        <a class="back" href="./">Back</a>
      </p>
      <p id="mv-status"></p>
      <input type="checkbox" id="do_stencil_buffer">stencil buffer</input>
      <input type="checkbox" id="do_antialias">antialias</input>
    </details>
  </header>
  <script type="module">
    import { WebXRButton } from '../js/util/webxr-button.js';
    import { Scene, WebXRView } from '../js/render/scenes/scene.js';
    import { Renderer, createWebGLContext } from '../js/render/core/renderer.js';
    import { CubeSeaNode } from '../js/render/nodes/cube-sea.js';
    import { InlineViewerHelper } from '../js/util/inline-viewer-helper.js';
    import { QueryArgs } from '../js/util/query-args.js';

    // If requested, use the polyfill to provide support for mobile devices
    // and devices which only support WebVR.
    import WebXRPolyfill from '../js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
    if (QueryArgs.getBool('usePolyfill', true)) {
      let polyfill = new WebXRPolyfill();
    }

    // XR globals.
    let do_stencil_buffer = document.getElementById('do_stencil_buffer');
    let do_antialias = document.getElementById('do_antialias');
    let xrButton = null;
    let xrImmersiveRefSpace = null;
    let inlineViewerHelper = null;
    let xrGLFactory = null;
    let xrFramebuffer = null;

    // WebGL scene globals.
    let gl = null;
    let renderer = null;
    let scene = new Scene();
    let is_multisampled_supported = false;
    let samples = 1;
    let mv_ext = null;
    let depthStencilTex = null;

    scene.addNode(new CubeSeaNode({ imageUrl: '../media/textures/cube-sea.png' }));
    scene.enableStats(false);

    function initXR() {
      xrButton = new WebXRButton({
        onRequestSession: onRequestSession,
        onEndSession: onEndSession
      });
      document.querySelector('header').appendChild(xrButton.domElement);

      if (navigator.xr) {
        navigator.xr.isSessionSupported('immersive-vr').then((supported) => {
          let mvCompat = testMultiViewCompatibility();
          if (!mvCompat) {
            document.querySelector('#mv-status').textContent = "❌ - Multiview Unsupported";
          } else {
            document.querySelector('#mv-status').textContent = "✔️- Multiview Supported";
          }
          xrButton.enabled = supported && mvCompat;
        });

        navigator.xr.requestSession('inline').then(onSessionStarted);
      }
    }

    function testMultiViewCompatibility() {
      let tempWebGLContext = createWebGLContext({
        xrCompatible: true,
        webgl2: true
      });

      return tempWebGLContext.getExtension('OCULUS_multiview') != null;
    }

    function initGL() {
      if (gl)
        return;

      gl = createWebGLContext({
        xrCompatible: true,
        webgl2: true
      });
      document.body.appendChild(gl.canvas);

      samples = gl.getParameter(gl.MAX_SAMPLES);

      mv_ext = gl.getExtension('OCULUS_multiview');
      if (mv_ext) {
        console.log("OCULUS_multiview extension is supported");
        is_multisampled_supported = true;
      }
      else {
        console.log("OCULUS_multiview extension is NOT supported");
      }
      if (!mv_ext) {
        mv_ext = gl.getExtension('OVR_multiview2');
        if (mv_ext) {
          console.log("OVR_multiview2 extension is supported");
        }
        else {
          console.log("Neither OCULUS_multiview nor OVR_multiview2 extension is NOT supported");
        }
      }

      function onResize() {
        gl.canvas.width = gl.canvas.clientWidth * window.devicePixelRatio;
        gl.canvas.height = gl.canvas.clientHeight * window.devicePixelRatio;
      }
      window.addEventListener('resize', onResize);
      onResize();

      // Set up a non-black clear color so that we can see if something renders wrong.
      gl.clearColor(0.1, 0.2, 0.3, 1.0);
    }

    function onRequestSession() {
      return navigator.xr.requestSession('immersive-vr', { requiredFeatures: ['layers'] }).then((session) => {
        xrButton.setSession(session);
        session.isImmersive = true;
        onSessionStarted(session);
      });
    }

    function onVisibilityChange(event) {
      console.log("Visibility change for "
        + (event.session.isImmersive ? "immersive" : "non-immersive")
        + " session: "
        + event.session.visibilityState);
    }

    function onSessionStarted(session) {
      session.addEventListener('end', onSessionEnded);
      session.addEventListener('visibilitychange', onVisibilityChange);

      initGL();

      if (session.isImmersive) {
        renderer = new Renderer(gl, true /* multiview */, do_antialias.checked);

        xrFramebuffer = gl.createFramebuffer();
        xrGLFactory = new XRWebGLBinding(session, gl);
        let layer = xrGLFactory.createProjectionLayer({
          textureType: "texture-array",
          depthFormat: do_stencil_buffer.checked ? gl.DEPTH24_STENCIL8 : gl.DEPTH_COMPONENT24
        });
        session.updateRenderState({ layers: [layer] });
      } else {
        renderer = new Renderer(gl);     

        let glLayer = new XRWebGLLayer(session, gl);
        session.updateRenderState({ baseLayer: glLayer });
      }
      scene.setRenderer(renderer);

      let refSpaceType = session.isImmersive ? 'local' : 'viewer';
      session.requestReferenceSpace(refSpaceType).then((refSpace) => {
        if (session.isImmersive) {
          xrImmersiveRefSpace = refSpace;
        } else {
          // In most samples moving forward we'll use this helper class rather
          // than the reference space directly to inject the necessary logic
          // for looking around an inline session with mouse and touch input.
          inlineViewerHelper = new InlineViewerHelper(gl.canvas, refSpace);
        }
        session.requestAnimationFrame(onXRFrame);
      });
    }

    function onEndSession(session) {
      session.end();
    }

    function onSessionEnded(event) {
      if (event.session.isImmersive) {
        xrButton.setSession(null);
      }
      renderer = new Renderer(gl);
      scene.setRenderer(renderer);
    }

    function onXRFrame(t, frame) {
      let session = frame.session;
      let refSpace = session.isImmersive ?
        xrImmersiveRefSpace :
        inlineViewerHelper.referenceSpace;
      let pose = frame.getViewerPose(refSpace);

      scene.startFrame();

      session.requestAnimationFrame(onXRFrame);

      scene.drawXRFrame(frame, pose);

      scene.endFrame();
    }

    initXR();
  </script>
</body>

</html>